Magnetic pulleys are used to initially separate or sort ferrous and nonferrous metal pieces from scrap material travelling on a conveyor belt. Separators of this type are disclosed in U.S. Pat. No. 4,869,811, issued to Richard B. Wolanski, et al., on Sep. 26, 1989, entitled "Rotor For Magnetically Sorting Different Metals," U.S. Pat. No. 3,448,857, issued to W. H. Benson, et al., on Jun. 10, 1969, entitled "Electrodynamic Separator," and U.S. Pat. No. 3,454,913, issued to A. F. Israelson, et al., on Jul. 8, 1969, entitled "Permanent Magnetic Pulley." Each of these patents describes a magnetic pulley wherein a number of rows of magnets are arranged in spaced relation on the rotor to produce an alternating magnetic polarity flux field.
In my earlier U.S. Pat. No. 5,207,330, entitled "Magnetic Pulley," granted on May 4, 1993, a magnetic repulsion separator is described for separating a mixture of discrete particles having various electroconductivity characteristics. The separator generally includes a main shaft, a pair of main bearings for supporting the shaft and a hollow rotor mounted on the shaft. The rotor having an even number of axially aligned notches around the outer perimeter thereof. A row of permanent magnets are aligned in each of the notches with each alternate row of magnets having opposite polarity. An outer magnetic shell is mounted for rotary motion on the main shaft and encircles the hollow rotor carrying the discrete particles of metals. A conveyor belt is mounted on the magnetic shell for rotary motion about the hollow rotor.